Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $88.39   5.392%   $93.156   $93.16   $93.15   $93.20  
  Purchase #2 $129.43   5.427%   $136.4542   $136.45   $136.45   $136.50  
  Purchase #3 $194.91   4.520%   $203.7199   $203.72   $203.70   $203.70  
  Purchase #4 $122.39   10.210%   $134.886   $134.89   $134.90   $134.90  
  Purchase #5 $165.99   8.637%   $180.3266   $180.33   $180.35   $180.30  
  Purchase #6 $109.68   12.394%   $123.2737   $123.27   $123.25   $123.30  
  Purchase #7 $183.34   10.496%   $202.5834   $202.58   $202.60   $202.60  
  7 purchase totals = $994.13       $1,074.3998   $1,074.40   $1,074.40   $1,074.50